BAGHDAD  A suicide bomber blew himself up outside a city council meeting in a town northeast of Baghdad on Thursday, killing 14 civilians during a four-day Islamic holiday, a morgue official said. The U.S. military said one soldier was killed and 10 were wounded.

An official with the Diyala hospital morgue in Baqouba, who asked not to be identified as he was not authorized to release the information, said 13 bodies were brought in to the morgue after the attack in the town of Kanaan, and that a wounded civilian later died.

A local policeman said on condition of anonymity as he was not authorized to release the information that at least 13 civilians were killed and 18 wounded in the Shiite-dominated town about 35 miles northeast of Baghdad.

The U.S. military gave a different casualty toll, saying one soldier and five civilians were killed, while 10 soldiers and one civilian were injured. The reason for the discrepancy in the death tolls was not immediately known.

The policeman also said the soldiers were handing out gifts to a group of people for the Eid al-Adha holiday when the attack took place. The military later denied the soldiers were handing out anything to civilians.

Meanwhile, U.S. soldiers carrying out operations in volatile Diyala province north of Baghdad found mass graves next to what they called a torture center where chains were attached to blood-spattered walls and a metal bed frame was still connected to an electrical shock system, the military said.

The discoveries in Diyala province near Muqdadiyah, about 60 miles north of Baghdad, came during a Dec. 8-11 operation that also saw multiple battles between U.S. troops and militants. The military said it killed 24 insurgents and detained 37 others in the operation.

The military said it thinks the site was run by al-Qaida in Iraq, and it was found based on tips from local Iraqis. Graves containing 26 bodies were found nearby.

"We discovered several (weapons) caches, a torture facility that had chains, a bed  an iron bed that was still connected to a battery  knives and swords that were still covered in blood as we went in to go after the terrorists in that area," said Army Maj. Gen. Mark P. Hertling, the top U.S. commander in northern Iraq.

Soldiers found a total of nine caches containing a surface-to-air missile launcher, sniper rifles, 130 pounds of homemade explosives and numerous mortar tubes and rounds, among other weapons.

Despite a nationwide decrease in violence of nearly 60 percent, Diyala province is still turbulent  largely because militants have been pushed into the area by the summer influx of U.S. troops in Baghdad, a freeze on activities by the Mahdi Army militia and the rise of Sunni anti-al-Qaida "awakening" groups.

"Yes, there are still some very bad things going on in that province," Hertling said. "We are slower in coming around because ... some of the extremists have been pushed east from Anbar province as they've seen the awakening movement there and north from Baghdad as the surge operations took place there."

Hertling noted, however, that the number of roadside bombings against coalition and Iraqi troops in the area had decreased between 40 and 50 percent since the summer. He said there were 849 such attacks in November, compared with 1,698 in June.

But he also warned that al-Qaida in Iraq was still capable of massive violence.

"You know, there's going to be continued spectacular attacks," Hertling said. "We're trying, along with the Iraq army, to protect all the infrastructure of Iraq. These people who are fighting us, who are fighting the Iraqi people, continue to just destroy with no intent to contribute to what Iraq is trying to be."

In Baghdad, shops were closed and the streets were empty as the Eid al-Adha holiday was observed.

Eid al-Adha is a holy celebration for Muslims, commemorating the prophet Abraham's willingness to sacrifice his son for God. According to Muslim tradition, after Abraham expresses his willingness, God sends the prophet two sheep instead for slaughter.

Violence this week has been down across Iraq  even in comparison with the recent drops in attacks  perhaps as a result of the holiday. On Wednesday, only one body was found in Baghdad and there was just one reported killing.

Separately, the U.S. military said that its preliminary investigation into a Dec. 17 incident in which a Marine killed an Iraqi policeman as they manned a joint security station north of Ramadi showed both men suffered cuts during a fight. It was not clear what sparked the altercation.

The military said the Marine, who was not identified and was treated at a hospital and released after the fight, was not yet facing charges, but that the investigation was ongoing.